CA2492978A1

CA2492978A1 - Medical implant

Info

Publication number: CA2492978A1
Application number: CA002492978A
Authority: CA
Inventors: Hans Henkes; Achim Flesser; Ronald Kontek; Juergen Speder; Ralph Bodenburg
Original assignee: Dendron Gmbh; Hans Henkes; Achim Flesser; Ronald Kontek; Juergen Speder; Ralph Bodenburg
Current assignee: Dendron GmbH
Priority date: 2002-07-19
Filing date: 2003-07-21
Publication date: 2004-01-29
Also published as: EP2781196A8; ES2641502T3; JP2005532887A; EP1542617A1; EP2415424A3; WO2004008991A1; US20140371839A1; AU2003254553A1; US8632584B2; JP2010264261A; EP2781196A2; JP5091985B2; EP2781196A3; EP2995282B1; US10342683B2; EP2995282A1; US7300458B2; DE10233085B4; JP4919217B2; US20080125855A1

Abstract

Disclosed is a medical implant which comprises a proximal and a distal end, is preformed so as to embody a superior structure at the place of implantation, and can be modified into a volume-reduced form in order to be inserted throu gh a microcatheter (22) and a guiding wire (21) that is disposed at the proxima l end. The implant (1) takes on the shape of a tube that is open in the longitudinal direction in the superior structure thereof and is provided wit h a mesh-type structure (3) of webs or filaments (2) that are interconnected. The proximal end of the implant (1) has a tapering structure (B) in which th e webs or filaments (2) converge towards a connecting point (5). Preferably, t he implant (1) represents a neurostent. The invention also relates to a system which is used for treating aneurysms or other vascular malformations and comprises such a medical implant that is detachably fixed to a guiding wire.

Description

DNDR0105 (27/05) AKI...
s The invention relates to a medical implant which is prefiom~ed in order to assume, at the site of implantation, a superimposed structure while, during the process of implantation, it is present in volume-reduced form.
Furthermore, the invention relates to the application of such an implant as a neuro-stent, its combination with a guide wire as well as a system for the ~o application of such implants when treating aneurysms or other vascular malformations.
It is known from prior art to treat vascoconstriction (stenoses) with the help of stents (vascular endoprostheses, vessel props) which are inserted into the stenotic area where they keep the vessel lumen open. ft is further known to use s such stents for closing off vessel wall ballooning (aneurysms) or fistulae.
For this purpose, balloon-dilatable stents are traditionally used. For placement these are crimped over a non-expanded balloon in non-dilated state, moved to the treatment location by means of a catheter system and then by expanding the balloon dilated and thus anchored within the vessel. Since there is no need for Zo sophisticated supporting and guiding sheaths when placing balloon-dilatable stents in position these can also be inserted into very fine vessels. It is, however, problematic that on account of their plastic deformability they can easily be compressed when external pressuns is exerted on them. Another disadvantage is encountered when anchoring such stents in that by applying as high pressure they have to be expanded initially beyond the circumferential size Z
they will finally have. Such an expansion beyond the circumferential size required may involve the risk of a vessel injury that may entail the formation of thrombs.
It is a further disadvantage of these traditional balloon-diiatable stems that due s to their structure they cannot simply be introduced through a laid micro-catheter and advanced to the implantation site but have to be arranged in the distal area of a specially designed micro-catheter in order to be capable of being moved to the implantation location by means of a so-called pusher. This calls fvr a rather sophisticated catheter technology that is difficult to handle. Another problem is o encountered in that a stent once placed in position can only be relocated or retrieved with great difficulty, if at all. After a wrongly placed stent has beers dilated it can neither be relocated nor removed as a rule.
It is further known to apply self expanding stents that are made of shape-memory materials. These possess a braid-like structure and are initially 1s introduced and moved in collapsed 'state through a catheter to the destination site where they expand either due to temperature changes (thermo-memory effect) or because the mechanical force exerted by the catheter (super-elasticity) is no longer effective. Such stents as well have the disadvantage in that the mechanisms required for their introduction are relatively expensive and space-Zo consuming. The known super-elastic expandable stents thus always require the use of a supporting and guiding sheath which results in a relatively large catheter size and, what is more, also makes it impossible to introduce such stents through an already laid catheter.
For the introduction into small-lumen intra-cranial vessels it is furthermore 25 known to use stents of shape-memory materials that initially are present in the form of an elongated f lament, and not before they exit from the catheter will they assume the tubular structure of a stent due to the change in temperature or because of the compression force no longer being exerted by the catheter.
From DE 197 03 482 A1 it is known far the treatment of aneurysms and similar 3 o diseases to use a scent consisting of two stretched out filaments that by the mechanical constraint of the strand are kept, induced by tension, in that stretched out form until when being pushed out of the catheter said constraint is removed and they assume the actual form of a stent. For the first time, this enabled the use of stents having shape-memory properties also in vessels of very small lumen such as the intra-cranial and cerebral vessel branches.
s Though well suited for certain applications these stents show a number of disadvantages in that, inter alia, it is relatively difficult to displace them inside the catheter and even impossible to move them back into the catheter, the latter being important in case of incorrect placements. Moreover, due to its very filigree structure the stent is hardly suited to cover aneurysms and fistulae in the io vessels In such a way that occlusion agents placed into them can be retained.
In view of the disadvantages associated with the state of the art it is thus the object of the invention to provide implants that can also be introduced through traditional micro-catheters into small-lumen intra-cranial vessels, are well placeable and relocatable, can be moved back into the micro-catheter in case of 25 need, and are suited to bridge vessel ballooning and fistulae in such a manner that these can be filled with occlusion agents. Furthermore, it would be desirable to have available implants capable of adapting to the vessel caliber relatively freely, i.e. must not be tailored to a specific vessel caliber.
According to the invention this objective is reached by providing a medical ao implant of the kind mentioned at the beginning that has the form of a longitudinally open tube with interconnected strings or filaments forming a mesh structure culminating, on one side, in a tapering structure at a connection point.
In other words, the implant according to the invention consists of a flat object that as a result of its impressed and superimposed structure assumes the form as of a slotted tube or hose with the free legs preferably overlapping. In its volume-reduced form it continues to be present in a curled-up condition, i.e. the diameter of the implant in volume-reduced state is significantly reduced in comparison to that of the superimposed structure. After the implant has been released it endeavors to assume the structure impressed on ft and expands to 3 o such an extent that the vessel surrounding the implant allows. Such an expansion in the form of an expanding spiral spring leads to the implant automatically adapting to the vessel caliber or lumen in such a manner that it can be applied in vessels having differrent calibers. In the case of narrow vessels this results in a relatively wide overlap of the two free legs, with wider vessels this overlap is smaller or even a free gap forms which in the event of vessel s branches may even be a desirable trait.
The implant proper has a mesh-like structure consisting of strings or filaments connected with each other. Strings occur if the implant comprises cut structures as, for example, are frequently put to use in coronary stents, a mesh-like structure consisting of filaments is found if the implants are present in the form io of mats having knitted or braided structures or in the form of individual filaments that are welded to one another.
An important aspect of the invention is that the implant is a flat or two dimensional structure that is rolled up to form a longitudinally open object capable of establishing close contact with the wall of the vessel into which it is ss introduced, The strings or filaments tapering on one side and culminating in a connection point permit the implant still to be connected to a guide wire to be easily retracted into the catheter in the event of an incorrect placement or inadequate adaptation to the implantation site so that it may be replaced by another implant 20 or reimplanted after the catheter has been repositioned. As a result of its tapering structure the implant entering the micro-catheter curls up more closely and again assumes its volume~reduced form with the pull force applied to the guide wire and the forces exerted via the catheter rim interacting.
In the catheter itself the implant is present in its volume-reduced form, z5 resembling rolled-up wire netting. Through the action of the guide wire and when thrust forcxs are applied an axial compression will be caused as well, and when released and the superimposed sttvcture is assumed a minor longitudinal contract'ron might occur. However, the longitudinal contraction noticed with dilatable stems will occur with the stents according to the invention to an 3o insignificant extent only.

The connection point of the medical implant situated at the end of the tapered structure serves at the same time as fastening point for the guide wire, either directly or via a connecting element. In the event of a cut or expanded metal foil this represents the point where the strings of the implant converge. (n the case s of a mesh-like structure consisting of individual filaments at least two filaments converge at this point and are connected with each other by welding or crimping.
The connection point usually serves also as a connecting element or part thereof which remains attached to the implant after the guide wire has been detached from the implant. It may be expedient to arrange this connection point io within a platinum spiral or attach it via a platinum spiral to a connecting element, said spiral may also serve as an x-ray reflecting marker for positioning purposes.
Especially preferred are connecting elements that are electrolytically corrodible, such as have been described in DE 100 10 840 A1 for example. Such connecting elements enable the implant, after it has been correctly positioned, to is be detached from the guide wire by applying etectrica) energy for brief periods of to 60 s for example.
As has already been explained the medical implant consists of a flat or two dimensional object that curls up into a hose as a result of the predetermined superimposed stnrcture. Preferably, this results in at least a slight overlapping of

2 o the free legs of the implant.
The implant proper may consist of a foil that is provided with appropriate string patterns, for example using laser technology methods. The string width amounts, for example, to 0.05 to 0.2 mm. The manufacturing technique is the same as that employed for tubular coronary stents.
a 5 Alternatively, expanded metal foil may be used with the respective string widths being of the same magnitude. In this case it is preferred to subsequently smooth the foil to make sure all strings are arranged on the same plane. The thickness of the foil usually ranges between 0.02 and 0.2 mm. Foils of greater thickness also permit the stent to be used in oth~r fields of application, for example as ao coronary stents yr in other regions of the body including for instance the bile duct or ureter.

The mesh width as a rule ranges between 0.5 and 4 mm and may vary within an implant. The same applies to the string width. !t is thus generally preferred to employ in the tapered area mesh sizes of greater width and length and/or greater string widths or thicker filaments. In the area of the tapering structure it is s normally not required to provide support for and coverage of the vessel wall, but on the other hand requirements as to tensile and thnrst strength increase.
In case mesh structures are used that are built from filaments warp-knitted or weft-knitted structures may be employed as well as filaments that are interconnected by welding. The filament thickness is normally in the range of between 0.01 and 0,1 mm and preferably between 0.02 and 0.076 mm. With respect to the mesh widths the aforementioned remarks shall apply.
To the extent that the mesh structure consists of individual filaments interconnected by welding a laser welding technique is preferably employed. A
knitted braiding of individual filaments is produced by generally known braiding, warp- or weft-knitting techniques as ate for example known in the field of wire mesh manfucturing or from textile technology. Especially preferred in this context are knitted braidings having a warp-knitting structure that, as a result of its manufacturing process, leads to curled-up rims because in this manner the superimposed structure can be produced with the help of the warp-knitting z o technique. Especially preferred is a warp-knitting structure known to the textile specialist under the German language term of "Fluse".
A special advantage of the medical implants according to the invention over the traditional expandable stents is that when adapting to the vessel to be treated a longitudinal contraction will no longer occur. The longitudinally open structure zs having a predetermined "winding" property has no effect whatsoever on the longitudinal expansion of the stent. The foil structures proper have been found to be remarkably true to size under the influence of thrust and tensile forces.
The same applies to the warp-knitted structure and the mesh-like structure consisting of individual filaments interconnected by welding.

Filaments consisting of a braid of individual strands and so to speak formed into a rope can also be employed. Braids comprising 12 to 14 strands having a total thickness of 0.02 mm have proved useful.
In case the superimposed structure cannot be impressed onto the implants with s the help of the warp or weft knitting method or by braiding, material may be put to use that possesses shape-memory properties. For example, such materials consist of alloys containing titanium and nickel which are known by the name of Nitinol, as well as iron and copper based alloys. Shape..memory properties may be based on a stress-induced martensitic transformation or a temperature-so induced martensitic transformation or may be the result of a combination of the two.
As materials for the filaments in particular it is also possible to use platinum, platinum alloys, gold and stainless steel. Generally speaking, all permanent implant materials known in medical technology can be employed that satisfy the relevant requirements.
As mentioned earlier the implants according to the invention in particular are also provided with x-ray reflecting markers that enable the positioning and implantation to be monitored. Such markers may have the form of spirals that are arranged proximally, in particular at the connection point of the strings or zo filaments. Preferably, the x-ray reflecting markers are also arranged at the distal end of the implant, particularly in the form of platinum or platinum/iridium elements incorporated in or attached to the mesh structure. In particular, the meshes of the implant according to the invention may at the distal end be provided with a lug or end in a lug that accommodates the marker element a s arranged levelly.
Furthermore, the invention relates to the combination of the above described implant with a guide wire that is linked to the distal end of the implant in a manner so as to be detachable. Such detachability is brought about, in particular, by means of an element that under the influence of electrical energy ~ o is capable of corroding, as is known from the prior art. Said guide wire is an otherwise commonly known and applied guiding wire of suitable kind for pushing the implant through a catheter to the site of implantation and, should it have been wrongly positioned, retract it into the catheter. It is clearly understood that the corrosion point may also be in the area of the guide wire proper or may be based on an otherwise known mechanical or thermal detachment technique.
s Eventually, the invention also relates to a system to be used for the treatment of aneurysms or other vascular malformations, said system comprising of a first micro-catheter, a first guide wire intended to bring the first micro-catheter in position, a second guide wire intended to move the implant through the first micro-catheter and place it in position as well as the implant that is arranged at the distal end of the second guide wire in a way so as to be detachable. Due to the curled up structure of the implant and as a result of making use of the combination with the guide wire it is possible after having placed the first micro cathetef to remove the first guide wire and introduce and handle the second guide wire which is provided with the implant. Previous 'implants of this kind ~.s were always introduced by using the so-called pusher technique that as a rule did not allow to recover the implant.
As per a preferred embodiment the system has additionally been provided with a second micro-catheter designed and intended to accommodate the second guide wire with the implant in such a way that it is slidable within said second a o micro-catheter and can be moved through the first micro-catheter to the target site. Coatings of the second micro-catheter that enhance its slidability may facilitate handling.
The first micro-catheter is per se a customary micro-catheter of a kind in widespread use, for example, in neuradiology and having a diameter/cafiber as ranging between 0.59 mm (20 mill and 0.3fi mm (14 mil).
Moreover, the system may have customary electrical components for the detachment by electrolytical means of the implant from the guide wire at a previously envisaged detachment location.
The invention is described in more detail by way of the figures as outlinEd below.

3 o They show:

Fig. l: An implant according to the invention having a honeycomb structure;
Fig. 2: another embodiment of a stent according to the invention having a honeycomb s structure;
Fig. 3: a third embodiment of a stent according to the invention having a honeycomb structure;
Fig. ~.: a warp-knitted structure as can be used for the implants according to the invention;
Fig. 5: a stent according to the invention together with guide wire and catheter;
Fig.6: schematic representation of an implant according to the invention shown in its superimposed and in its volume-reduced shape;
Fig. 7: a marker element as can be used in the system according to the invention;
Fig.8: schematic reptesentation of two a o detachment locations by means of which the implant according to the invention can be detachably linked to a guide wire.
The implant according to Figure 1 consists of a mesh or honeycomb structure that in the present case comprises of a multitude of filaments interconnected a5 with the help of the laser welding technique. The implant can be subdivided into the functional portion A proper and the tapering proximal structure B, the two being distinguishable, inter alia, by a different mesh size. To enable the functional portion A tv perform its retaining function its meshes 3 are held relatively narrow so that they lend themselves to the retention of occlusion s o spirals arranged in an aneurysm. !n the tapering proximal part B of the implant there is provided a wider mesh structure 4 which has been optimized towards having a minimum occlusion effect. In the area of the tapering structure 2 the filaments preferably have a greater thickness to be able to better transfer to the functional portion A the thrust and tensile forces of the guide wire exerted at the connection point 5 when the implant is introduced and placed in position. The s filament thickness in the functional part A generally ranges between 0.02 and

4.076 mm, in part B this is between 0.076 mm and above.
The proximal part B preferably forms an angle from 45° to 120°
at connection paint 5, in particular an angle of about 90°. The filament thickness (or string width} same as the mesh size and shape may vary over a great range to suit so varying requirements as to stability, flexibility and the like. Then= is no doubt that the proximal part as well contacts the vessel waA and thus does not interfere with the flow of blood within the vessel.
At the distal end the filaments 2 end in a series of "tails" 6 that are of suitable kind to carry platinum markers that facilitate the positioning of the implant.
Having assumed its superimposed structure the implant 1 is curled up in such a way that the edges 7 and $ are at least closely positioned to each other, preferably overlap in the area of the edges. In its volume-reduced form the implant 2, similar to a wire mesh roll, has curled up to such an extent that the roll so formed can be easily introduced into a micro-catheter and moved within said 2o catheter. Having been released from the micro-catheter the Curled-up structure springs open and attempts to assume the superimposed structure previously impressed on it and in doing so closely leans to the inner wail of the vessel to be treated thus superficially covering a fistula, vessel branch or aneurysm that exists in that location. In this case the extent of the "curs up " is governed by the 2 s vessel volume; in narrower vessels a greater overlap of the edges 7 and $
of the implant 1 will occur whereas in wider vessels the overlap will be smaller or even ,underlap', will be encountered, and due care must be exercised to make sure the implant still exhibits a residual tension.
Suitable materials that can be employed are alloys having shape-memory 3 o properties. The finished product is subjected to a tempering #reatment at temperatures customarily applied to the material so that the impressed structure is permanently established.
Figure 2 shows another embodiment of a stent 1 according to the invention having the above described honeycomb structure where the tapering proximal s part B is connected with the functional part A by means of additional filaments 9 in the peripheral area 10 as well as in the central area. Such additional filaments 9 and 10 bring about a mare uniform transmission of the tensile and thrust forces from the proximal structure B to the functional part A so that the tensile forces can be better transmitted, especially if the stent might have to be 1 o repositioned by having to be retracted into the micro-catheter. This will facilitate the renewed curling up of the stent. Similarly, the transmission of thrust forces occurring when the stent is moved out and placed in position is facilitated so that the stent can be gently applied. Moreover, it is pointed out that identical numbers apply to identical positions.
15 Figure 3 shows another embodiment of a stent 1 according to the invention having a honeycomb structure with the edges 7 and 8 being formed of filaments 9 that for the main part run straight. According to this embodiment the thrust or pressure exerted by the guide wire at point 5 is very directly transmitted to the edges 7 and 8 of the functional stent part A which further increases the effect zo described with reference to figure 2.
The embodiment as per figure 3, same as those depicted in figure 1 and 2, may be based on a cut foil, i.e. the individual filaments 2, 9 and 10 are substituted by individual strings (land) being the remaining elements of a foil processed with the help of a cutting technique. Laser cutting techniques far the production of zs slants having a tubular stnrcture are known and have been frequently described.
The processing of a fail for the production of a pattern suitable for a stent is pertormed analogously. The impression of the superimposed structure is carried out in the same way as is used for the filament design version.
Foils worked with the help of a suiting technique are preferably finished by 3 o electrochemical means to eliminate burr and other irregutacities, achieve a smooth surface and round edges. Such working processes of electrochemical nature are known to the expert and already are in widespread and extensive use in medical technology. In this context it is to be noted that the stents according to the invention that are based on a two-dimensional geometry and on which a three-dimensional structure is impressed subsequently can be manufactured s and processed more easily than the conventional ,tubular' stems that already during manufacture have a three-dimensional structure and necessitate sophisticated and costly working processes and equipment.
As painted out above the mesh structure of the implant according to the invention may consist of a braiding of individual filaments. Such a knitted zo structure is shown in figure 4 where the individual filaments 2 are interwoven in the form of a 'single jersey fabric' having individual loops 3 forming a mesh-like structure 11. Single jersey goods of this type are produced in a known manner from a row of needles. The single jersey goods have two fabric sides of diff~rent appearance, the right and left side of the stitches. A single jersey fabric material ~s features minor flexibility in transverse direction and is very light.
It is considered especially advantageous to have the fabric rims of such a knitted structure curling up as is known, for example, from the so-called "Fluse"
fabric (German term) which is of benefit with respect to the superimposed structure and application dealt with here. In this case the superimposed structure can be zo impressed by means of the knitting process. However, the use of shape-memory alloys in this case as well is feasible and useful.
For the production of such knitted structures known knitting processes and techniques can be employed. However, since the implants according to the invention are of extremely small size - for example have a size of 2 by 1 cm --it 25 has turned out to be beneficial to produce the implants in the framework of a conventional warp or weft knitting fabric of textile, non-metallic filaments, for example in the form of a rim consisting of the respective metallic filaments from which the weft or warp knitting fabric either starts out or that extends from such a fabric. The arrangement of the metallic part of the weft or warp knitting fabric 3 o at the rim is of significance with a view to achieving the aforementioned curling effect. The non-metallic portions of the knitted fabric are finally removed by incineration, chemical destruction or dissolution using suitable solvents.

Figure 5 shows a combination of a guide wire 21 with implant 1 attached to it that consists of filaments 2 connected to each other by welding. Clearly evident from the figure are the distal ends 6 and the connection point 5 where the filaments of the implant converge in a tapering structure and that simultaneously s represents the joining location with guide wire 21. The guide wire 21 is introduced into a micro-catheter 22 which is of customary make.
Shifting the guide wire 21 within the catheter 22 will cause the implant 1 to be pushed out of or drawn into the catheter. Upon the stent being pushed out of the micro-catheter the mesh-like structure attempts to assume the superimposed io shape impressed on it, when being drawn in the mesh structure folds back into the micro-catheter adapting to the space available inside.
As a result of the stiffness of its mesh structure the implant can be moved to and fro virtually without restriction via the guide wire 21 until it has been optimally positioned within the vessel system.
is As mentioned earlier customary micro-catheters can be used. The advantage of the implant according to the invention and of the combination of implant and guide wire according to the invention is, however, that after having placed the micro-catheter in position with a customary guide wire/marker system the combination of guide wire 21 and implant 1 according to the invention can be Zo introduced into the micro-catheter, moved through it towards the implantation site and then moved out and applied in that position. Alternatively, it will be possible to have a second micro-catheter of smaller caliber accommodate guide wire 21 and implant 1 and with this second micro-catheter within the firstly positioned micro-catheter shift them to the implantation site. In any case, the zs implant can be easily guided in both directions.
Fig. 6 shows a schematic representation of an implant according to the invention in its superimposed and in its volume-reduced shape; In its expanded shape as illustrated in Figure 6a the implant 1 forms a ring-shaped structure with slightly overlapping edges 7 and 8. The figure shows the implant 1 from its proximal end 3o as a top view with the connection point 5 being approximately positioned opposite to the edges 7 and 8. In the combination according to the invention the guide wire 21 is affixed at the connection paint 5.
Figure 6a shows the same implant in its volume-reduced form as it is arranged, for example, in a micro-catheter in curled up condition. In the case illustrated s there is a total of two windings of the curled-up implant 7 with the connection point 5 being located at the proximal side and the two lateral edges 7 and 8 being the starting and final points of the roll or spiral. The structure is held in 'rts volume-reduced form by the micro-catheter 22; when the implant 1 is pushed out of the micro-catheter 22 it springs into its expanded shape as illustrated by ~o Figure 6a, similar to a spiral spring, Figure 7a shows a marker element 12 suitable far the implants according to the invention with said element being capable of being arranged at the distal end of the implant 1. The marker element 12 consists of a "lug° 13 provided with a small marker plate i 5 levelly arranged inside it (flush with the plane of the implant without any projecting elements), said plate being made of an x-ray reflecting material, for example platinum or platinum-iridium. The marker plate 15 is connected to the surrounding implant structure by means of laser welding techniques.
Figure 7b gives an example of the arrangement of the marker elements 12 at so the distal end of the implant 1 (refer to item 6 in Figure 1).
Figure 8 is a schematic representation of two variants of a separating arrangement 8a and 8b via which the implant according to the invention is detachably connected to a guide wire. In both cases the separating arrangement 23 consists of a dumb-bell shaped element that dissolves under the influence of as electrical energy when in contact with an electrolyte. At the proximal (guide-wire side) end of the dumb-bell shaped element 23 as per Figure 8a a spiral structure 25 is located that interacts with a strengthening spiral 26 of the guide wire.
At the distal end a ball-shaped element 27 is arranged that with the help of a laser welding technique is connected to a platinum spiral 28 which in tum is linked 3o with the connection point 5 situated at the proximal end of the implant.
The is platinum spiral 28 also serves as x-ray reflecting proximal marker of the implant 1.
To strengthen the joint between the ball-shaped element 27 and the connection point 5 a reinforcement wire 29 may prove expedient. Alternatively, the platinum spiral 28 may also be designed in such a manner that it withstands the tensile and thrust forces imposed on it.
For the separating element 23 especially a steel material may be useful that susceptible tv corrosion in an electrolyte under the in~uence of electrical energy.
To accelerate contusion and shorten the separating time span a structural or Zo chemical weakening of the dumb-bell may be beneficial, for example by applying grinding methods or thermal treatment.
Generally, the portion of the dumb-bell 23 accessible to the electrolyte has a length of 0.1 to 0.5 mm, particularly 0.3 mm.
The spiral structure 25 is secured via welding spots both to the dumb-bell ~.s shaped element 23 and the reinforcement spiral 26 of guide wire 21. The guide wire 21 itself is slidably accommodated within the micro-catheter 22.
Fig. 8b shows a second embodiment that differs from the one described by Fig.
8a in that the dumb-bell shaped element 23 has a ball-shaped element 27 at both ends, said elements being connected distally to the connection point 5 of ~o the implant and proximally to the guide wire 21 via spirals 28 and, respectively, 26.
It is of course also provided that other separating principles may be applied, for example those that are based on mechanics) principles or melting off plastic connecting elements.
a s - Claims -

Claims

1. Medical implant, having a proximal and a distal end, that is preformed to assume a superimposed structure at the implantation site but can be made to take on a volume-reduced form making it possible to introduce it by means of a micro-catheter (22) and a guide wire (21) arranged at the proximal end, characterized in that the implant (1) in its superimposed structure assumes the farm of a longitudinally open tube and has a mesh structure (3) of interconnected strings or filaments (2), said implant showing a tapering structure (B) at its proximal end where the strings or filaments (2) converge at a connection point (5).

2. The implant according to claim 1, characterized in that it consists at least to some extent of an alloy having shape-memory properties.

3. The implant according to claims 1 or 2, characterized in that the volume-reduced form is a structure curled up similarly to a spiral spring.

4. The implant according to one of the above claims, characterized in that the tapering structure (B) ends in the connection point (5) arranged centrally.

5. The implant according to claim 4, characterized in that the structure converges in a platinum spiral (28).

6. The implant according to one of the above claims, characterized in that it consists of cut foil curled up to form a longitudinally open tube.

7. The implant according to any one of the claims 1 to 6, characterized in that it consists of an expanded metal foil curled up to form a longitudinally open tube.

8. The implant according to any one of the claims 1 to 5, characterized in that it consists of individual filaments (2) interconnected by welding to form a mesh structure.

9. The implant according to any one of the claims 1 to 5, characterized in that it consists of a mesh braiding of individual filaments (2).

10. The implant according to claims 8 or 9, characterized in that the filaments (2) comprise individual strands worked into a rope-like structure.

11. the implant according to claim 9, characterized in that the mesh braiding has a knitted structure that due to the manufacturing methods employed results in curled up edges (7, 8).

12. The implant according to claim 11, characterized in that the knitted structure is a fabric known by the German term "Fluse".

13. The implant according to claim 11, characterized in that the edges (7, 8) of the longitudinally open tube are provided so as to overlap.

14. The implant according to any one of the above claims, characterized in that it has one or several markers (12) at its distal end.

15. The implant according to claim 14, characterized in that the one or several markers (12) are arranged at the ends of the junction points of the strings or filaments (2).

16. Neuro-stent according to any one of the above claims.

17. Use of an implant according to any one of the claims 1 to 15 as neuro-stent for closing off vessel wall ballooning, fistulae or vessel branching.

18. Combination of guide wire and implant according to any one of the claims 1 to 16 having the implant (1) detachably arranged at the distal end of the guide wire (21).

19. The combination according to claim 18, characterized in that the guide wire (21) is provided, at its distal end, with a platinum spiral (26) connected to the implant via a connecting element (23) that under the influence of electrical energy is corrodible.

20. The combination according to claim 19, characterized in that the electrically corrodible connecting element (23) is arranged between a distal platinum spiral (26) of the guide wire (21) and a proximal platinum spiral (28) of the implant (1).

21. System for the treatment of aneurysms or other vascular malformations for use with a first micro-catheter (22);
a first guide wire for the placement of the first micro-catheter (22);
a second guide wire (21) intended to move an implant (1) through the first micro-catheter (22) and place said implant into position: as well as an implant (1) according to any one of the claims 1 to 16 that is detachably arranged at the distal end of the second guide wire (21).

22. The system according to claim 21, Characterized in that the implant (1) is connected to the second guide wire (21) via an electrolytically corrodible element (23).

23. The system according to claim 21 or 22, characterized in that said system is provided, additionally, with a second micro-catheter that has been designed and is intended to accommodate the second guide wire (21) with the implant (1) in such a way that it is slidable within said second micro-catheter and can be moved through the first micro-catheter to the target site.

24. The system according to any one of the claims 21 to 23, characterized in that it is provided with additional devices to bring about the electrical corrosion of the connecting element.

25. The system according to any one of the claims 21 to 24, characterized in that the implant (1) having been discharged from the micro-catheter (22) assumes the superimposed structure impressed on it to the extent predetermined by the dimensions of the surrounding vessels.